1. Field of the invention
The present invention relates to a method for effecting pressure development of a latent image on a photosensitive and pressure sensitive sheet, herein-after referred to as the photo-and-pressure sensitive sheet.
2. Description of the prior art
There is a generally known photo-and-pressure sensitive sheet that includes a first sheet coated with pressure-rupturable capsules containing chromogenic dyestuff and a second sheet coated with a developer. Hereinafter, this double sheet will be referred to as the composite sheet. The first sheet bears a latent image resulting from the exposure to light, and is overlaid with the second sheet. Finally the composite sheet is pressed together. As a result of this pressure the capsules rupture and the dyestuff flows out. The dyestuff colors together with the developer on the second sheet, thereby forming a colored image on the second sheet. The pressing of the sheets is performed by a pair of press rollers.
However, pressure development requires a high pressure to be applied to the composite sheet. Here arises a problem; that is, when the press rollers receive the composite sheet and release them, their torque is likely to change suddenly due to the thickness of the composite sheet inserted between the rollers. Especially when the press rollers receive the forward end of the sheet the change is large, and likely to spoil the forward end portion of the latent image. Even if the spoiled portion is in a small area of the image, it will be a fatal defect to the quality of the image.